1. Field of Invention
The present invention relates to a frit-based hermetic sealing system for glass plates, seal materials, processes to apply these seal materials, seal designs for selective and controlled absorption of light to heat and seal the system. These hermetic seals are useful in various applications such as (a) encapsulating solar cells based on silicon, organic systems, and thin film, (b) encapsulating other electronic devices such as organic LEDs (OLED), and (c) architectural windows and automotive glass.
2. Description of Related Art
Laser sealing is a widely investigated selective sealing process. Conventional frit-based laser sealing process involves absorption of an Infra-Red (IR) laser light by an absorber such as pigment or colored frit in the seal system. Accordingly, the IR absorption (i.e., heating) occurs at the top interface—the interface between glass plate and the seal material. Owing to the thickness and mass of material to be heated, the amount of heat supplied must be relatively high. Conventional laser sealing processes involve absorption of IR radiation by an appropriate pigment or colored frit in the sealant material. Deposited seals are typically about 60% or less of their theoretical density before melting/sintering. Therefore, significant dimensional changes are to be expected during laser processing to form the seal (or any related localized energy deposition process). The process can be time consuming because such a large mass of material must be heated and is not trouble free. For example, conventional frit based laser sealing material includes an organic binder which can provide contamination within the sealed glass from combustion of the binder upon heating, large voids and bubbles that could reduce the strength of the seal. Since most of the heat is generated at the glass/seal material interface the process is more prone to cracking of seal and the glass plate. Similar such problems arise in other selective sealing processes where IR, visible or UV lights are used for sealing.
Accordingly, improvements in the art of selective sealing processes such as laser sealing are required.